Rising Sea Level

NEW! - 2/19/10 Rising sea, stronger storms hammering West Coast shorelines 07/20/2011

See photos of extreme high tides, which illustrate the possible impacts of rising sea levels.

Coastal land underwater with sea level rising

As global temperatures rise, the oceans warm slightly and expand, ice caps and glaciers melt, and more precipitation falls as rain instead of snow. This causes sea levels to rise. Most climate change models forecast a global sea-level rise of half a meter (over 1½ feet) by 2100.

Globally, sea levels rose four to ten inches in the last century. Researchers expect sea levels to continue rising.

With over 2,300 miles of marine coastline, much of Washington’s population lives, works, and thrives in coastal areas. Coastal communities are particularly vulnerable to the effects of climate change, which puts much of the state’s population at risk – homes, infrastructure, livelihoods, and even lives.

Coastal climate change effects include:

Sources: Impacts of Climate Change on Washington's Economy (University of Oregon) pg 65

Return to top

Coastal community flooding

More information from Ecology

Melting glaciers, ice fields and polar ice caps, plus warming ocean waters all contribute to rising sea levels. Washington’s shoreline gives the state a large exposure to the risks of rising sea levels, higher tides and storm surges.

For instance, South Puget Sound between Tacoma and Olympia is more vulnerable to early flooding than Seattle. Low-lying agricultural areas such as Willapa Bay and Skagit River Delta will be among the first areas affected.

Climate change is predicted to bring stronger storms with heavier precipitation and higher wave conditions. This will increase the frequency and extent of flooding in many of Washington's communities.

Sources: Impacts of Climate Change on Washington's Economy (University of Oregon) pg 65

Coasts – King Co. Climate Conference 2005 (University of Washington - Climate Impacts Group

Climate Impacts on Coasts of Pacific NW, Doug Canning & Phil Mote; MIT press - in review – abstract not yet available)

Return to top

Coastal erosion & landslides

More information from Ecology

Climate change is predicted to increase storm intensities and wave height in the Pacific Ocean. More frequent, intense storms combined with higher overall sea levels will result in higher coastal erosion rates and more storm damage. Coastal communities will face increased property damage to infrastructure (such as roads and water treatment systems).

Heights of storm waves off the Oregon and Washington coast have measured as much as 8 feet higher than 25 years ago. Such waves deliver 65% more force when they come ashore.

Erosion, washouts and landslides can destroy property and transportation systems.

Source: Impacts of Climate Change on Washington's Economy (University of Oregon) pg 68

Return to top

Seawater intrusion in wells

A higher sea level means saltwater may penetrate wells in low-lying communities. This will reduce the availability of freshwater for coastal communities.

Islands pose unique challenges for ground water management. Island County’s ground water aquifers are recharged only by rainfall. This area is in the rain-shadow of the Olympic Mountains, and areas of Island County receive between 17 to 40 inches annually. Some aquifers (such as those at or below sea level near shorelines) are connected to Puget Sound saltwater. Portions of these aquifers may contain saltwater. Seawater intrusion, the movement of marine saltwater into freshwater aquifers, could become a serious problem.

(Click each image to see and enlargement)

For more saltwater intrusion information:
Island County Water Resource Management Plan, Final Draft June, 2005

Is Seawater Intrusion Affecting Ground Water on Lopez Island, Washington? USGS

Return to top

Lost wetlands and estuaries

Wetlands often occur in low-lying areas and rising sea levels may convert these valuable habitats to deep water.

Wetlands and estuaries:

Sources: Puget Sound Action Team: Climate – Uncertain Future, pg. 20, 29

Sustaining our remaining wetlands for people, fish and wildlife – Issue up Close (Washington Department of Ecology) p 7